An “atypical” form of mad cow disease has been found in an 11-year-old beef cow in Alabama. Luckily, this is the form that is not dangerous to humans, and the disease was detected before the animal was slaughtered.

This is only the fifth case of this particular disease confirmed in the US, though the second in Alabama. Alabama authorities are calling it a “rare and spontaneous” event, which is consistent with some studies and data from the Centers for Disease Control.

Mad cow disease is a fatal neurodegenerative disease that affects the central nervous system of cows. There are two types: the atypical form — like the type found in Alabama and which can happen “spontaneously” — and the classical form, which is usually spread through feed when cows eat contaminated food. The classical form is the dangerous strain, since humans eating infected cows have been known to develop Creutzfeldt-Jakob disease, a fatal brain disorder. This is also the form that was the target of the “mad cow scare” that started in the United Kingdom in the 1980s. In the United States, fear over mad cow caused cattle prices to drop, and in 2003, a single case of mad cow in Washington state was enough to cause several countries to ban beef imports from the US.

It is still unclear exactly what causes mad cow disease, though the main theory is that it’s caused by dangerous proteins called prions that develop in the brains of cows. The Alabama case was caught due to surveillance protocols established by the US Department of Agriculture in 2009. These protocols were established due to fear over previous cases, and consist of screening cows that show physical symptoms of the disease (like changed temperature and loss of coordination) and sending these cows for further tests instead of allowing them to be slaughtered. Of the four previous cases in the US, only one of them was of the classical form, and said cow was imported from Canada.